CN102756552B - Shading process when task is changed - Google Patents

Abstract

The invention relates to a method for controlling ink volumes by means of a control computer in an inking unit of a printing press (1), wherein the supply of ink volumes is temporarily increased during a printing run compared to normal requirements. The invention is characterized in that the color difference of two consecutive printing jobs is calculated by means of the control computer and the color difference is adjusted during these two printing jobs by temporarily changing the supply of ink quantities.

Description

Color correction method when the task is changed

technical field

The invention relates to a method for controlling the ink volume with a control computer in an inking unit of a printing press, in which the supply of the ink volume is temporarily increased during a printing run compared to the normal requirement.

Background technique

Such a method for controlling the amount of ink in a printing press is known from laid-open document DE 100 56 247 A1. This relates to a method for controlling ink volumes in different inking zones of a printing press inking unit, wherein the ink volumes are quickly adjusted in the different inking zones, wherein adjacent inking zones are also set as far as possible. It is possible to quickly achieve its stable ink volume. This is achieved in that, in the different ink zones of the printing press, a setpoint value for the ink quantity is preset for each ink zone in a time-dependent manner; so that the values of the ink streams output by the ink sources for the ink zones correspond accordingly each rated value for the amount of ink; and when said rated value should be kept constant for a zone (Zone) in the ink zone by outputting from said ink source an ink flow corresponding to said rated value To maintain a constant ink volume and to change the ink volume in a predetermined ink zone when the setpoint value for the ink zone changes from a first value to a second value, by determining a correction ink flow, The correction ink flow is adjusted to the sum of the correction ink flow and the second target value over a transition time interval. This has the result that, when the setpoint value of the ink quantity changes while the printing press is running, an increased ink quantity is briefly supplied to the inking unit. Feeding of an excessively high amount of ink may also be referred to as "toning". However, this method is only suitable for speeding up the change of the setting parameters during a printing job during printing operation in order to avoid transition times and thus also avoid waste pages.

Contents of the invention

It is now the object of the present invention to provide a method for controlling the amount of ink with a control computer in a zonal inking unit of a printing press, which allows printing jobs to be carried out even between two printing jobs The required ink volume is also achieved more quickly when changing.

According to the invention, this task is solved by the invention. Advantageous embodiments of the invention emerge from the further description and the figures. In the method according to the invention, the control computer is programmed in such a way that it first calculates the coloring difference of two successive print jobs based on the print theme of the two print jobs and by temporarily increasing the supply of ink volumes between the two The coloration differences are corrected between print jobs. This means that between the two printing jobs, initially the required ink is supplied more quickly and the excess ink is reduced more quickly.

In a first embodiment of the invention, it is provided that the supplied ink quantity is increased at the start of the second print job if there is too little ink. In this case, more ink is supplied at the start of printing of the second print job than is required for the completion of this print job. As a result, the desired coloring of the second print job can be achieved more quickly by briefly increasing the ink supply at the start of the second print job.

In a further refinement of the invention it is provided that, in the event of too much ink, the supplied ink quantity is increased at the end of the first printing job. In this way, the excess ink on the remaining printing material is reduced by increasing the ink consumption at the end of the first printing job, for example when the printing press is running down, and thus a faster reduction of the excess ink between two printing jobs is achieved.

A great advantage of the method according to the invention is that between two printing jobs all the ink does not have to be removed from the inking unit first and must then be reconstituted for the second printing job.

Furthermore, it is proposed that the dampening medium supply be switched off by the control computer for a short time interval at the beginning of the printing of the second printing job when a very large amount of ink is removed and that all are switched on again after the time interval has elapsed. The above-mentioned wetting medium is supplied. The removal of the ink is considerably accelerated by temporarily shutting off the dampening medium supply.

Furthermore, it is proposed that the control computer selects the matching method on the basis of a comparison of the print images of the first and second print jobs. The control computer compares the contents of the print images of two subsequent print jobs with one another and determines whether and in which ink zone more or less ink is required. Depending on the ink requirement determined in this way, either a method for reducing excess ink or a method for increasing the ink supply is carried out for the relevant ink zone. The adjustment process can be carried out automatically or the printing operator first receives corresponding advice displayed on a screen and can then take predetermined measures by means of actuation. This considerably simplifies the work of the printer, since the printing supply does not have to calculate and select the matching method itself.

In a particularly advantageous configuration of the invention, it is provided that the control computer performs a print job change between the first print job and the second print job when the printing material format of the second print job is lower than the printing material of the first print job. When the object size is small, the areas that are no longer printed in the case of the second printing job are taken into account. It can be printed in a variety of formats on sheet-fed presses. For example, printing in format 105, format 75 and format 52 is thus possible on a sheet-fed printing press. When first printing with a large format, such as format 105, and then printing a sheet of format 75, there are ink areas that are no longer printed in the edge regions of the inking unit and printing unit, so that the ink does not appear in these ink areas. reduce. This overinking is taken into account by the control computer in such a way that the final printing is compensated for by the lateral ink leveling and by the corresponding combination of the "toning" (increasing color) in the event of a large format reduction. Transitions on the marginal zone (randzonen) of . In this way, the ink is removed in the non-printed ink regions and the removed ink is supplied to the printed edge regions. In this case, the excess ink in the non-printed ink regions is used to temporarily increase the ink supply in the printed edge regions. Only correspondingly less ink then has to be fed into the inking unit in order to increase the ink.

Description of drawings

The invention is described and explained in detail below with the aid of a number of figures. The accompanying drawings show:

FIG. 1 shows a plurality of adjustment processes of the inking unit when changing printing jobs according to the prior art and shows the improved method according to the invention on the far right;

Fig. 2 is the structure of the ink layer on the inking device roller in the inking device from the first ink distribution roller to the ink application roller; and

Figure 3 is the relationship between the amount of ink and the surface overlapping ratio.

detailed description

FIG. 1 shows three printing methods—print V1 , print V2 and print V3 , which can be carried out in the printing press 1 when a print job is changed. These three methods have been disclosed in the prior art. In this case, when a print job is changed, it is first checked whether the ink curve needs to be lowered, and if necessary, the printing forme is replaced and a so-called ink entry 2 is carried out. If the ink curve does not need to be lowered, the printing plate is likewise replaced and it checked whether the inking unit has to be washed. If the inking unit needs to be cleaned, a so-called ink entry 1 is carried out. If there is no need to wash the inking unit, then go directly to the printing step. It is now proposed according to the invention to convert the adjustments on the printing press 1 caused by the change of printing jobs into corresponding color changes. Based on the color change, the control of "toning" takes place with a short-term increased ink input. This has the great advantage that the printer does not have to think about the necessary coloring changes. That is, in the first method V1 it must be ensured that the ink curve is lowered before the printing plate is changed. But printers often forget to trigger this function. This results in printing until the stack of sheets is complete and then no more sheets can be printed for the lowering of the ink curve. Variant 2 has the great disadvantage that the washing of the inking unit is very time-consuming and entails additional costs, since on the one hand the ink is consumed and on the other hand the washed-off ink has to be disposed of to waste. The main disadvantage of method 3 is the high start-up waste when processing the second print job.

FIG. 2 shows the basic structure of the ink layer in the inking unit, where it can be seen that the ink quantity consists of a basic layer 2 proportional to the printed layer thickness and of ink wedges 3 depending on the surface overlap. The ink wedge 3 is strongest on the first anilox roller in the vicinity of the ink fountain and descends onto the base layer 2 towards the last ink application roller on the plate cylinder.

The relationship between the surface overlapping ratio FD and the thickness of the ink layer can be seen in FIG. 3 . A corresponding ink volume FA is assigned to the ink layer thickness. This means: Ink volume goes from 1 to about 1.25 for face overlap from 0 to 100%.

The relationship between the ink volume FA in the inking unit and the surface overlap FD for a constant print layer thickness can be determined either by means of a simulation program (eg FASI) or by printing tests. Furthermore, the ink volume FA in the inking unit is directly proportional to the printed layer thickness. Based on the area overlap FD of the old print job and the new print job, the relative ink volumes in the inking unit are calculated for the new job. The relative ink volumes are converted to relative coloration. Then, by means of toning (color enhancement) and/or ink entry 2 and/or surface subtraction when printing is started to compensate for the relative shading.

An example is:

80% surface overlap FD of the ink zone/ink key (Farbzone) for the first printing job.

For the second printing task, the surface overlapping ratio FD of 40% in the same ink area.

The following values can be read from the table in Figure 3:

Ink volume 80% FD = 1.2; ink volume 40% FD = 1.1

For the second print job, an overinking of 1.2/1.1=1.09 results in a print job change. This means that 9% of the ink volume must be removed from the ink zone when the second print job is started. According to the prior art, this is done by said toning.

Other options are also possible:

Ink can be fed in or removed as necessary before printing. Ink zones that require more ink at start-up than the first printing job can obtain this ink before the first printing, for example by means of ink entry 2 . That is to say, for these inked areas no toning is required during printing and the inked areas are therefore stabilized earlier in ink.

It is also possible for the method to suggest or carry out automatically. Based on the comparison of the image content of the first and second printing jobs, the machine control can automatically execute suitable methods or suggest at least one control option to the printing operator.

The method of the present invention can also be used with surface subtraction combined. If a lot of ink has to be removed in the area of the ink keys during a job change, so that the toner has to overrun, for example, more than 100 sheets, the dampening medium supply can therefore be switched off when the second printing job is started Several turns in order to significantly speed up the removal of the ink by means of so-called surface subtraction. After the surface subtraction, the dampening unit is automatically switched on again by the control computer of the printing press 1 and a modified ink feed or toning is carried out. The modified color palette then acts on all ink zones.

The following examples are cited for this:

80% surface overlap rate FD in the ink area 1 of the first printing task

The first printing job is in the ink zone 2 with 8% surface overlapping ratio FD

The second printing task is 8% surface overlap rate FD in ink zone 1

80% surface overlapping ratio FD of the second printing job in ink zone 2

Read from the graph in Figure 3:

Ink volume 80% FD = 1.2

Ink volume 8% FD = 1.02

When starting the second printing job, approximately 18% of ink must be removed for ink zone 1 and approximately 18% of ink must be added for ink zone 2.

The amount of ink stored in the inking unit (here now simply calculated for all ink zone areas) is approximately 20 mm ³ /mm. The amount of ink stored actually depends on the area coverage, see above. With each facet subtracted, one removes about 0.8 mm ³ /mm of ink in simplified calculations. That is if one performs eg a three-face subtraction, about 3*0.8 mm ³ /mm/20 mm ³ /mm = 12% of ink is removed.

This means that in this example, a short ink adjustment must also be carried out for ink zone 1 in order to remove 18%-12%=6% of the ink. 18%+12%=30% of ink must be supplied to ink zone 2, which can either be supplied by one type, ink entry 2, before or after surface subtraction, or by toning. Supplying ink is always easier and better than removing ink.

But this method has limitations. This method presents problems in the case of larger format changes, if the replacement is performed by a larger sheet format. These area subtractions are also critical with smaller substrate formats. This must be considered accordingly to the proposed method. There is therefore a further concept in which, in the case of format reductions, areas not to be printed are taken into account. In the case of a large format reduction, the effect of the reduction in format can be compensated for by lateral ink distribution and by a correspondingly combined excessive toning in the edge region of the final print.

An example is also given for:

First print job, gauge 105, all 32 ink zones have a face overlap FD of 40%.

The second print job only uses ink zones 3 to 30 , that is to say, ink zones 1 and 2 and 31 and 32 are not printed. The ink regions 3 to 30 have a surface overlapping ratio FD of 80%, and the other ink regions have a surface overlapping ratio of 0%.

It can be read from the table in Figure 3 that:

Ink volume 80% FD = 1.2; ink volume 40% FD = 1.1; ink volume 0% FD = 1.0

That is, about 10% of the ink must be removed in the non-printed ink areas and about 10% of the ink must be added in the printed ink areas. But because do not carry out ink lowering in the edge zone that does not print, ink zone 3 and 4 and ink zone 29 and 30 use the ink of the edge zone that does not print, thereby make in these ink zone 3 and 4 and 29 and 30 do not carry out ink lowering. Color enhancement (+10% - 10% = 0%).

List of reference signs

1 printing press

2 base layer

3 Ink wedge depending on FD

FD surface coincidence rate

FA ink application amount

V1 First variant of print job change

V2 Second variant of print job change

V3 Third variant of print job change

Improved variant of V4 print job change

Claims (6)

1. A method for controlling the amount of ink in an inking unit of a printing press (1) with a control computer, wherein the supply of the amount of ink is temporarily increased during a printing run compared to the normal requirement, which It is characterized in that the color difference of two consecutive printing jobs is calculated by means of the control computer and the color difference is adjusted between these two printing jobs by temporarily increasing the ink supply, wherein the The increase in the delivery of the ink quantity takes place at the start of the second print job in the case of too little ink, and the increase in the delivery of the ink quantity takes place at the end of the first print job in the case of too much ink. 2. The method according to claim 1, characterized in that the dampening medium supply device is switched off by the control computer at short intervals at the start of printing of the second printing job in the case of removing a very large amount of ink and that After the time interval has elapsed, the dampening medium supply device is switched on again. 3. A method according to claim 1 or 2, characterized in that the control computer selects the matching method based on a comparison of the print images of the first and second print jobs. 4. The method according to claim 1 or 2, characterized in that, when the control computer performs printing job replacement between the first printing job and the second printing job, the substrate specification of the second printing job is lower than that of the first printing job. The substrate size hour takes into account areas that are no longer printed in the case of a second print job. 5. The method according to claim 4, characterized in that the excess ink of the smaller format is distributed laterally by the distribution roller in the inking unit of the printing press (1) and is output too high to the edge area of the final printing ink to compensate. 6. A method according to claim 5, characterized in that the non-printed ink areas output their excess ink to the printed edge areas.